A vehicle may include a heat pump for heating and cooling a passenger compartment. The heat pump may include a compressor for pressurizing refrigerant. The refrigerant may travel throughout the heat pump system and transfer heat between two or more different locations. The lubricant used in the compressor may be mixed with the refrigerant and the lubricant may travel throughout the heat pump system. Over time, lubricant may attach itself to the inner walls of the heat pump components, such as heat exchangers and refrigerant lines. This may reduce the amount of lubricant available to the compressor, resulting in compressor degradation. Further, lubricant may reduce the heat transfer characteristics of the heat exchangers. Lubricant may accumulate in components other than the compressor while the compressor is running during normal operation of the system. Further, lubricant may accumulate throughout the heat pump system while the compressor is off as refrigerant migrates due to temperature gradients between the various components of the refrigerant subsystem. An oil separator may be used to delay lubricant accumulation in refrigerant subsystem components away from the compressor, but the undesirable conditions associated with lubricant accumulation persist.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for a vehicle heat pump, comprising: selecting a heat pump flushing mode in response to a vehicle being electrically coupled to a stationary power grid; and flushing the vehicle heat pump via activating a pump.
By activating a pump of a heat pump system, it may be possible to provide the technical result of flushing lubricant from locations in a heat pump system where lubricant is undesirable to locations where lubricant is desired. Consequently, heat pump efficiency may be improved. In one example, the pump may be activated when the heat pump has not operated for a predetermined amount of time while a vehicle in which the heat pump is located is electrically coupled to a stationary power grid. The stationary power grid may allow the heat pump to flush lubricant from refrigerant subsystem components where it is not desired without draining a vehicle battery.
The present description may provide several advantages. In particular, the approach may improve heat pump efficiency. Additionally, the approach may improve heat pump durability. Further, the approach may provide different approaches to flushing a heat pump of lubricant.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.